I've been likely my MotoActv. Like Raging, I picked one up to replace my FR305. And I've had the opportunity to see it evolve through the various software updates.
When I first got it, battery life was extremely poor. ~3-4hrs, without music or bluetooth. After updates 5 and 6, that seemed to be resolved. With simple GPS running, I'd say it gets close to 9 hrs of use. Though, when I did my 50M, it conked out around 7:11 but it spent half that run searching GPS signal. So, I'm not going to call that the be all, end all for battery life.
It seems to lock GPS quicker than my FR305 ever did, and hold it in places the Garmin couldn't as well.
The Actv is more fragile than the FR305 though, if I dropped my FR305 on the pavement, it'd like be fine. If I dropped the Actv on the pavement, unless it landed perfectly, it'd shatter. 🙁
The MotoActv is my primary watch, and with me on nearly every run. Its had a few times where its conked out on my during the run, but only a couple times. Usually a reboot fixes that though . . . I usually go weeks between reboots, if not months.
I think the UI and set up is far easier on the Actv than the Garmin. On the FR305, I never used many of the more advanced features because setting them up was a PITA. On the Actv, its cake.
Also, I like that I can pop the Actv out of the wrist and arm mounts so that they can be cleaned easily.
The motoactv.com website is also extremely good, compared to Garmin. Which has no such online tracking site. But the Garmin has Garmin Connect to easily sync to most fitness sites though. The Moto can only post to FB and Twitter natively.
Bottom line for me? I like it, and look forward to seeing future revisions of it. There's a lot of potential in devices like this. The hardware and OS is capable of a lot, when properly designed.